Process for the production of a smoking fluid for smoking foodstuffs

ABSTRACT

A process for treating foodstuffs with a smoking fluid produced by contacting finely divided wood chips or sawdust with superheated steam. Oxygen, air enriched with oxygen or a mixture of oxygen and inert gas may be introduced in conjunction with the superheated stream or may subsequently be introduced into the smoking medium withdrawn from the thermally decomposed wood chips. The smoking fluid is then either brought directly into contact with the foodstuff to be treated to impart the desired smoke flavoring thereto or it may be converted into a liquid phase for subsequent use.

United States Patent Inventor Gerhard Fessmann Mozartstr l6, Fellback, Stuttgart, Germany Appl. No. 797,279 Filed Feb. 6, 1969 Patented Jan. 11, 1972 Priority Feb. 8, 1968 Germany P 16 92 1 16 .7

PROCESS FOR THE PRODUCTION OF A SMOKING FLUID FOR SMOKING FOODSTUFFS 8 Claims, No Drawings U.S. Cl. 99/229, 99/259 Int. Cl A231) 1/04, A23b 3/04 Field of Search 99/229,

Primary Examiner-Hyman Lord Attorney-Thomas M. Marshall, Esq.

ABSTRACT: A process for treating foodstuffs with a smoking fluid produced by contacting finely divided wood chips or sawdust with superheated steam. Oxygen, air enriched with oxygen or a mixture of oxygen and inert gas may be introduced in conjunction with the superheated stream or may subsequently be introduced into the smoking medium withdrawn from the thermally decomposed wood chips. The smoking fluid is then either brought directly into contact with the foodstuff to be treated to impart the desired smoke flavoring thereto or it may be converted into a liquid phase for subsequent use.

PROCESS FOR THE PRODUCTION OF A SMOKING FLUID FOR SMOKING FOODS'IUFFS This invention refers generally to the production of a smoking medium for the smoking of foodstuffs, such as fish, meat, sausage, ham, cheese, etc.

Included in the prior art are numerous ways of smoking foodstuffs, and the production of smoking mediums suitable for that purpose. Up to the present time in most cases it has been the usual practice to produce the smoking medium through the dry distillation, the vacuum distillation, or the open flame combustion of wood, or sawdust. The prior art processes render it difficult to produce smoking mediums with uniform characteristics, such that smoked good produced at one plant but smoked at different times do not vary considerably in taste. Further, the prior art processes often produce soot which is carried by the smoking medium thereby contaminating the smoking equipment and often impairing the appearance of the smoked foodstuffs.

More recently, to avoid these and other drawbacks of the prior art, it has been proposed in my copending application Ser. No. 5l5,l26, filed Dec. 20, 1965 now U.S. Pat. No. 3,462,282 issued Aug. 19, 1969 to introduce superheated steam above 180 C. into sawdust or the like for the production of a smoking medium. The fluid thereby produced can be used as a smoking medium in gaseous form, or after cooling may be used in a liquid phase. In that process, the smoking medium is produced without combustion of the wood particles or sawdust. The instant invention presents an improved form for carrying out that process wherein the superheated steam may have mixed therein normal air or a neutral gas.

ln comparison with the prior art previously discussed, this process has substantial advantages. Herein, is disclosed a simple method for producing a smoking medium of high-grade quality and having constant smoking characteristics, and in particular, having a uniform content of aroma-imparting, conserving and color-imparting substances. The temperature during the production of the smoking medium is kept uniform and the process may be carried out independently of fixed connections, for example, without a connection to a chimney. It is readily possible to precisely regulate the moisture content and the density of the smoking medium. Further, the smoking medium is free of, or is at least low in, carcinous substances, so that effects detrimental to health are avoided. Because of the relatively high moisture content obtainable in a smoking medium generated with the use of steam, it may be liquified more easily than the previously known smoking mediums. Particularly, it may be liquified at temperatures of over 0 C. Further advantages are obtained since it may be condensed directly out of the gaseous phase upon the goods being smoked, whereby the smoking time is considerably shortened.

The primary object of this invention is to provide an improved process in which smoking mediums are obtained through the action of superheated steam on wood particles or the like.

A further object of this invention is to produce the smoking medium in such a way that its composition, from the viewpoint of taste, is always uniform, and may be repeatedly produced with the same composition, free of soot, and have a particularly mild smoked taste.

These and other objects, advantages and features of the invention will become more apparent from the following description of the preferred embodiment.

Briefly, the method of this invention includes the production of a smoking medium for smoking foodstuffs through the action of superheated steam on a reaction material in particle form, preferably finely divided wood chips or the like. The superheated steam is introduced into the reaction material, and the thus-formed gaseous smoking medium, laden with effective substances, is transferred out of the reaction material situated in a first reaction zone and into a second reaction zone where further conversions of the effective substances occur. It

riched with oxygen, or a suitable mixture of oxygen and inert gas. Consequently no air of normal composition is supplied. Normally in the second reaction zone there are no particulate wood solids.

The smoking medium formed in the first reaction zone emerges therefrom with a relatively high temperature of at is in accordance with the invention, that into at least one of least to C. Therefore the effective substances which impart the typical smoked smell and smoked taste in the smoking medium after leaving this first reaction zone, may undergo still further conversions, so that the second reaction zone is normally located directly downstream of the first reaction zone and normally does not contain said particulate wood solids. The second reaction zone terminates at a point where the smoking medium has cooled down to a temperature at which no conversion of the effective substances worth mentioning occurs.

After leaving the second reaction zone in a gaseous phase, the smoking medium may be brought into contact with the foodstuff that is to be smoked. Or it may be caused to condense on the foodstuff that is to be smoked, through which, among other things, the smoking time is considerably shortened. Or else in many cases, it may be advantageously cooled down until it is converted into its liquid phase, and be used as a liquid smoking medium.

The reaction material is preferably in the form of wood particles having a thickness of approximately 0.5 to 4 mm., and a length of approximately 2 to 10 mm., and may be in the form of sawdust or wood chips. It is also noted that any other material may be used which upon thermal reaction with steam yields a smoking medium similar to that obtained from wood.

One particular advantage of the process disclosed herein is that there is contained in the smoking medium less materials having an acrid or sharp smell and taste. This enables the smoke-treated foodstuffs to be flavored with a particularly mild and pleasant smoked taste.

It is believed that the acrid smell of smoking mediums is to be ascribed to acids, among others to formic acid and acetic acid. It is recognized that these acids have a conserving effect, so that a certain content of them is desirable, but on the other hand, too great a quantity which is evident through their acrid or pungent taste, is not compatible with good health. An excess of these substances leads to denaturization of the albumin of the smoked wares. It is known that overly intensive smoking causes the wares to shrink, which may be ascribed in a large part to the effect of the described substances. These disadvantages also are avoided by the process disclosed herein.

The pure oxygen, air enriched with oxygen, or the mixture of oxygen and inert gas, may with advantage be added to the steam before its entry into the first reaction zone. The reaction in this first reaction zone then occurs in direct association with the formation of liberation of the materials forming the smoking medium and at a comparatively high temperature, i.e., at the temperature prevailing in the reaction material. This leads to a particularly intensive influencing of the composition of the smoking medium. The addition of the oxygen component may take place either before or after the superheating of the steam.

Alternatively, the oxygen, the air enriched with oxygen, or the mixture of oxygen and inert gas, may be mixed with the previously produced smoking medium in the second reaction zone. On occasion, both measures may be combined. Through the addition of the oxygen-containing gas in the second reaction zone, it is also possible to influence the moisture content of the gaseous smoking medium in a manner so that it may be produced in a relatively dry form. Because the smoking medium, directly after its emergence out of the reaction material, has a temperature of at least 100 to 140 C. the reactions produced by the oxygen take place with satisfactory rapidity.

The useage of oxygen or air enriched with oxygen is simple to accomplish and most attractive from the economic point of view. Under special circumstances, however, it may be beneficial to use other mixtures of oxygen and inert gas. ln general, by inert gas there is meant those gases which do not participate materially in the reactions that occur and thus do not themselves influence the formation of the smoking medium. Further, the inert gas does not affect the smoking process itself in a detrimental manner. Therefore, when reference is made to inert gas it is of secondary importance whether the said gases are actually completely inert. This can scarcely be established with definiteness with the complicated, intricate and sofar-unexplained phenomena of such smoking treatments.

Regarding the lower limit for the quantity of oxygen, it has been found that even with quite small quantities of pure oxygen, or with a comparatively moderate enrichment of air with oxygen, e.g., 25 to 30 percent by volume of a definite improvement in the effect of the smoking medium is obtained with respect to smell and taste. In general, the air enriched with oxygen, or the mixture of oxygen and inert gas, should contain at least 0.5 percent by volume, and preferably about 4 percent by volume, more oxygen than is normally contained in air. With oxygen and inert gas mixtures other than air, the inert gas can be made approximately equivalent to the amount of nitrogen in air.

The production of the smoking medium is preferably a continuous process wherein the reaction material is conveyed continuously through the first reaction zone, and the fluid producing the reaction is introduced continuously into the reaction material. It has been found to be advantageous for a deficiency of oxygen to be introduced into the reaction zone concerned. Through varying the total quantity of oxygen used and the degree of the enrichment by oxygen in the case of an oxygen-air mixture or of a mixture of oxygen and inert gas, the degree of oxidative alteration of the smoking medium, and thus the degree of the alternation in the mildness of the smell and taste, may be adapted to the desires and requirements of the food under treatment. This may be maintained both from one smoking operation to the next, and also during the course of one continuous smoking operation.

The method disclosed herein may be carried out in equipment that is of itself known. The thickness of the layer of reaction material in the first zone may, for example, be provided in an amount of 4 to ID cm. in height.

The advantages obtained by the process disclosed herein are particularly surprising when considering the case of mixing in normal air alone, that is, without additional or without pure oxygen, wherein a comparable smell and milder taste is not .possible. Particularly surprising is that even with the addition of small quantities of oxygen, a definite improvement is obtained. Such a difference, in comparison with the behavior of air, was found to be totally unexpected.

By supplying oxygen to the first reaction zone the process can be carried out in different ways. According to a first aspect of the invention, it is provided that the reaction in the first reaction zone proceeds without the development of open flame or visible combustion, i.e. without the development of a flame or glow. The temperature of the fluid introduced into the first reaction zone to produce the smoking medium should be no higher than approximately 390 C. This process may also be provided when the oxygen component is introduced into the second reaction zone.

According to a second aspect of the invention, it is provided that the formation of the smoking medium, occurring in the first reaction zone, is effected with visible or open flame combustion. For this purpose, the fluid introduced into the first reaction zone containing superheated steam also contains a quantity of oxygen sufficient to maintain visible combustion. The temperature of the fluid should be above the ignition point of the reaction material and below approximately 700 C. Each proces has its advantages and produces smoking mediums of different taste and smell. They are both, however, very mild, and may be produced free of soot. Each of the two methods will be described hereinafter in greater detail.

A. Reaction in the First Zone without Development of Open Flame Combustion The reaction in the first reaction zone proceeds endothermically, with the fluid effecting the conversion of the reaction material generally having a maximum temperature of about 390 C. lts lower temperature should be at least 180 C. and preferably at least 250 C. The smoking medium produced is free of soot.

The quantity of oxygen introduced depends to a certain extent on the point of introduction and on the nature of the gas mixture. it also depends on the intensity of influencing the smell and taste desired. In the case of the preferred admixture of oxygen, oxygen-enriched air, or oxygen and inert gas, with the steam prior to entry into the reaction material, the mixture ratio is preferably within the range of approximately 0.5 to 5 parts by volume of total oxygen to parts by volume of steam. With this admixture the upper limit is determined in accordance with the type of gas and with the requirement that no visible combustion of the reaction material shall occur, viz, that the reaction shall proceed without a development of light and thus without a glow or the formation of a flame. When pure oxygen mixed with steam is used, prior to passage through the reaction material, it is possible, while meeting these requirements to add in general up to about 3.5 parts by volume of oxygen to l00 parts by volume of steam. When oxygen-air mixtures, or oxygen and inert gas mixtures are used, then, because of the inhibiting action of the nonreactable portion of gas, there may be mixed a somewhat greater quantity of oxygen, preferably up to about 5 parts by volume of oxygen to 100 parts by volume of steam. It is only when the addition of oxygen is beyond the given limits that visible combustion appears, provided the temperature is above the ignition point of the reaction material.

B. Reaction in the First Zone with Visible or Open Flame Combustion This process also avoids the drawbacks of the prior art processes wherein sawdust is burnt with a development of light in the production of a smoking medium. With prior art processes and contrary to the process of the invention, it is among other things difficult to control the course of the combustion, or to regulate it, so as to have constant conditions. Because the taste of the smoked goods depends on the smoking medium, and this in turn depends on the combustion process, and in particular on the combustion temperature, it has up to the present time scarcely been possible to create even approximately uniform smoking conditions. Furthermore, as a result of the great quantity of waste gas when operating with chimneys, prior art processes lead to contamination of the atmosphere, and are also detrimental from the economic point of view. Moreover, with the prior art processes, there occurs an unpleasant acrid" or sharp" smell in the smoking medium which causes a more or less great impairment of taste of the treated smoked goods when an insufficient supply of air or only slight oxidation is present. A considerable formation of undesirable soot also occurs. The method of operation provided herein avoids these and other drawbacks.

Using the process disclosed herein avoids the formation of soot even in the case of visible combustion. The reasons for this have up to the present time not been completely known. It may, however, be assumed that by means of the steam the combustion temperature in the reaction material is kept low. There may also be additional unknown causes. It has been found that with the processes of the invention no complete combustion of the wood particles to ashes occurs, rather there is left behind a black carbonlike granulated residue, which can be burnt again in air. Then soot becomes produced, while smoke-active substances are no longer formed.

The added quantity of oxygen depends to a certain extent on the composition of the added gas, on the tendency of the individual reaction materials to fonn soot, and on the desired intensity of influencing the smell and taste. It has been found that the exothermic conversion and visible combustion of the reaction material, when it consists of wood or of a material having similar characteristics, peat for example, ordinarily begins when with 100 parts by volume of superheated steam there is mixed about 3.5 parts or more by volume of pure oxygen. In the case of mixtures of oxygen and inert gas, or of air enriched with oxygen, because of the inhibiting effect of the nonreactable portion of gas, use must be made of somewhat greater quantities of oxygen, for example, a total of 4 to 5 parts by volume of oxygen being present in 100 parts by volume of steam. lt is, however, possible, depending on the requirements of individual cases, also to add considerably greater quantities of oxygen or of oxygen-containing gas, while taking into account the requirement that not too high a temperature shall exist in the reaction material. Because such increase in the quantity of pure or enriched oxygen causes higher cost, from the point of view of economy and of the oxygen gas available in individual cases, there will ordinarily be added notmore than is needed for maintaining uniform combustion without forming soot, while producing a mold smoking medium having the smoking effect desired for individual cases. Ordinarily 6 to 12 parts by volume of oxygen to 100 parts by volume of steam is sufiicient.

With an admixture of oxygen, or of an oxygen-containing gas introduced into the second reaction zone, i.e. into the previously produced smoking medium after it emerges from the reaction material, there exists no such limitation with respect to the quantity of oxygen. The transfer of the mixture of superheated steam and oxygen or oxygen-containing gas is done at a temperature above the ignition point of the reaction material in the case concerned. This ignition point may when using particles of wood vary from case to case depending on the nature and the composition of the reaction material. During this process it is sufficient that the fluid introduced into the first reaction zone be heated, for starting up, to a temperature above the ignition point of the reaction material; later on, if desired, operations may be conducted at a lower temperature, provided that uniform combustion is obtained. The supply temperature, in combination with the steam: oxygen: inert gas ratio, makes possible simple and good control of the progress of the process. Because of the combustion phenomena the temperature in the reaction material rises, however, because of the great proportion of steam, uniform and gentle combustion is obtained.

C. Other Considerations The process of the invention, as a result of the possibilities of variations which have been discussed relative to the oxygen content of the introduced gas, to the location or locations where the gas is introduced, to the temperature during the formation of smoking medium, and so forth, facilitates easy adaptation to individual requirements and desires. The optimum conditions for each individual case, within the scope of the variables discussed above, may be established easily by those carrying out the process, on occasion by simple preliminary tests. It is, moreover, also possible to adapt and regulate the process during the smoking operation itself.

The process disclosed herein results in an entirely uniform smoking fluid when the oxygen, or oxygen-containing gas and superheated steam are supplied uniformly. The smoking medium can be repeatedly produced at any desired point of time with the same composition. The smoking medium is also free of soot. It has a mild smell, an leads to products having an excellent taste, with the mildness of the smoking medium and of the product being reproducible. The smoking medium may be transferred by condensation onto the wares that are to be smoked, and may be liquified through cooling down to temperatures above 0 C. This means a combination of advantages, not obtainable with the previously known processes.

Although the preferred embodiment of the invention has heretofore been described, it is to be recognized that other modifications and variations may be made without departing from the spirit and the scope of the invention.

What is claimed is:

1. A process of producing a smoking fluid for smoking foodstuffs which comprises the steps of contacting particulate wood solids with superheated steam at a temperature in the range between 180 390 C. to effect a thermal decomposition of said wood solids and form a smoking fluid, withdrawing the smoking fluid from said wood solids, and introducing during at least one of the aforesaid steps an oxygen-containing gas selected from the group of oxygen, air enriched with oxygen or a mixture of oxygen and an inert gas wherein the amount of oxygen is approximately 0.5 to 5 parts by volume to parts of steam by volume whereby thermal decomposition of the wood solids occurs without any open flame combustion.

2. The process of claim 1 wherein said wood solids form a first reaction zone during the production of said smoking fluid, a second reaction zone is provided downstream thereof where further conversions of the effective substances of the smoking fluid occur, and into at least one of said reaction zones is introduced an oxygen-containing gas.

3. The process of claim 1 wherein said oxygen-containing gas is introduced into said wood solids in combination with the introduction of said superheated steam therein.

4. The process of claim 3 wherein said oxygen-containing gas is mixed with the steam prior to the superheating thereof.

5. The process of claim 1 wherein said oxygen-enriched air or mixture of oxygen and inert gas contains at least 0.5 percent by volume more oxygen than the normal oxygen content m air.

6. The process of claim 1 wherein said oxygen-enriched air or mixture of oxygen and inert gas contains at least 4 percent by volume more oxygen than the normal oxygen content in air.

7. The process of claim 1 wherein said superheated steam introduced into said wood solids is at a temperature of at least 250 C.

8. The process of claim 1 wherein said superheated steam introduced into said wood solids contains mixed therewith a maximum of about 3.5 parts of oxygen by volume to 100 parts ofsteam by volume. 

2. The process of claim 1 wherein said wood solids form a first reaction zone during the production of said smoking fluid, a second reaction zone is provided downstream thereof where further conversions of the effective substances of the smoking fluid occur, and into at least one of said reaction zones is introduced an oxygen-containing gas.
 3. The process of claim 1 wherein said oxygen-containing gas is introduced into said wood solids in combination with the introduction of said superheated steam therein.
 4. The process of claim 3 wherein said oxygen-containing gas is mixed with the steam prior to the superheating thereof.
 5. The process of claim 1 wherein said oxygen-enriched air or mixture of oxygen and inert gas contains at least 0.5 percent by volume more oxygen than the normal oxygen content in air.
 6. The process of claim 1 wherein said oxygen-enriched air or mixture of oxygen and inert gas contains at least 4 percent by volume more oxygen than The normal oxygen content in air.
 7. The process of claim 1 wherein said superheated steam introduced into said wood solids is at a temperature of at least 250* C.
 8. The process of claim 1 wherein said superheated steam introduced into said wood solids contains mixed therewith a maximum of about 3.5 parts of oxygen by volume to 100 parts of steam by volume. 